. Creating a part container
Over the next eight pages you build a butt hinge: two leaves with interleaving knuckles, a pin through them, and a joint that swings the hinge open and shut.
. Creating a basic sketch
The leaf starts as a rectangle: 30 mm wide, 60 mm along the pin axis, centred on the origin so the pin axis runs through the middle of one edge. You draw it with the Rectangle tool; the constraints that make it exactly that size are written for you, and one more pins it to the origin.
. Applying 3D features
The outline becomes a leaf in seven features: the plate, one screw hole, the hole repeated into a row, rounded corners, one knuckle, the knuckle repeated along the pin axis, and the bore for the pin. Every feature is a dialog or a pick tool on the toolbar, and every one adds a row to the History panel and a statement to the file.
. Defining connectors
A connector is a named coordinate frame attached to a part's geometry. Joints are built between connectors, so a part declares them where other parts will attach: on the pin axis, for a hinge leaf. The frame's Z axis is the axis a revolute joint turns about and a slider travels along.
. Exporting the part
A part is exported from the top bar. The fixed leaf goes out as STEP for other CAD tools and as STL for printing.
. Inserting the part into an assembly
An assembly is a .assembly.js file. It holds no geometry of its own: it inserts parts from other files, grounds one of them, and joins the rest with joints. This page inserts the three hinge parts.
. Adding joints
A joint (a mate in the code) connects two connectors and leaves some motion free. The hinge needs two: a revolute joint between the leaves' knuckle connectors, which leaves rotation about the pin axis free, and a fastened joint that locks the pin into the fixed leaf.
. Applying animation to a joint
Revolute and slider joints can be driven through their range from the Joints panel. Nothing is written to the file: the animation is a viewport tool.